Cassini Sees Heat Below the Icy Surface of Enceladus

A masterpiece of deep time and wrenching gravity, the tortured surface of Saturn’s moon Enceladus and its fascinating ongoing geologic activity tell the story of the ancient and present struggles of one tiny world. This is a story that is recounted by imaging scientists in a paper published in the journal Science on March 10, 2006.

The enhanced color view of Enceladus seen here is largely of the southern hemisphere and includes the south polar terrain at the bottom of the image.

Ancient craters remain somewhat pristine in some locales, but have clearly relaxed in others. Northward-trending fractures, likely caused by a change in the moon’s rate of rotation and the consequent flattening of the moon’s shape, rip across the southern hemisphere. The south polar terrain is marked by a striking set of `blue’ fractures and encircled by a conspicuous and continuous chain of folds and ridges, testament to the forces within Enceladus that have yet to be silenced.

The mosaic was created from 21 false-color frames taken during the Cassini spacecraft’s close approaches to Enceladus on March 9 and July 14, 2005. Images taken using filters sensitive to ultraviolet, visible and infrared light (spanning wavelengths from 338 to 930 nanometers) were combined to create the individual frames.

The mosaic is an orthographic projection centered at 46.8 degrees south latitude, 188 degrees west longitude, and has an image scale of 67 meters (220 feet) per pixel. The original images ranged in resolution from 67 meters per pixel to 350 meters (1,150 feet) per pixel and were taken at distances ranging from 11,100 to 61,300 kilometers (6,900 to miles) from Enceladus.

Image credit: NASA/JPL/Space Science Institute

Cassini Sees Heat Below the Icy Surface of Enceladus

A new study in the journal Nature Astronomy reports that the south polar region of Saturn’s icy moon Enceladus is warmer than expected just a few feet below its icy surface. This suggests that Enceladus’ ocean of liquid water might be only a couple of miles beneath this region — closer to the surface than previously thought.

The excess heat is especially pronounced over three fractures that are not unlike the “tiger stripes” — prominent, actively venting fractures that slice across the pole — except that they don’t appear to be active at the moment. Seemingly dormant fractures lying above the moon’s warm, underground sea point to the dynamic character of Enceladus’ geology, suggesting the moon might have experienced several episodes of activity, in different places on its surface.

The finding agrees with the results of a 2016 study by a team independent of the Cassini mission that estimated the thickness of Enceladus’ icy crust. The studies indicate an average depth for the ice shell of 11 to 14 miles (18 to 22 kilometers), with a thickness of less than 3 miles (5 kilometers) at the south pole.

“Finding temperatures near these three inactive fractures that are unexpectedly higher than those outside them adds to the intrigue of Enceladus,” said Cassini Project Scientist Linda Spilker at NASA’s Jet Propulsion Laboratory, Pasadena, California. “What is the warm underground ocean really like and could life have evolved there? These questions remain to be answered by future missions to this ocean world.”